Kidney disease can be caused by a variety of insults, ranging from inherited gene defects, damage caused by disease of other organ systems (such as diabetes, immune disorders), infections, or exposure to toxic chemicals. Kidney disease can be secondary to other systemic diseases, such as hemolytic uremic syndrome, Lupus nephritis, or high blood pressure. Inherited kidney disease can be caused by mutations in genes expressed by renal tubular epithelial cells, the cells which line the collecting ducts of the kidney. Mutations that affect these cells cause cellular dysfunction, disorganization and death of these cells with resultant cyst formation. Such diseases are common potentially lethal genetic disorders in humans. Poly cystic kidney disease (PKD) is an example of such diseases and is one of the most common inherited diseases in humans. Twenty million Americans (1 in 9 adults) have chronic kidney disease. Autosomal dominant PKD (ADPKD) affects between 1/500 and 1/1000 people, or 500,000 Americans alone, and results in cystic and tubular overgrowth that leads to destruction of the normal kidney architecture and renal failure Mutations in PKD1 account for 85% of the cases of ADPKD; mutations in PKD2 account for the remaining 15% of ADPKD. The latter disease affects 75,000 Americans.
There are no treatments available for PKD and many other chronic kidney diseases. People with such diseases feel fatigued, develop high blood pressure and anemia, and often suffer from pain and weak bones. When kidney disease progresses to kidney failure, individuals require dialysis or kidney transplant in order to survive. While some experimental reagents are in early stage clinical trials, the mainstay of treatment, especially for ADPKD, is supportive care. Ultimately, individuals with end-stage kidney disease must go on dialysis or receive a kidney transplant.
The rare inherited macular degeneration Malattia Leventinese (ML), also known as Doyne honeycomb retinal dystrophy (DHRD), is an autosomal dominant disorder characterized by the formation of deposits called drusen between the retinal pigment epithelium (RPE) and Bruch's membrane by middle age. During the latter stages of the disease, pathology, such as decreased visual acuity, geographic atrophy, pigmentary changes, and choroidal neovascularization can become apparent. The characteristics of ML have much in common with age-related macular degeneration (AMD), a heterogeneous disorder which is the leading cause of blindness in the elderly in the developed part of the world (4, 5), affecting more than 20% of the population age 65 and over.
A single mutation (R345W) in the EGF-containing fibrillin-like extracellular matrix protein 1 (EFEMP1) gene on chromosome 2 is responsible for the ML phenotype in humans. The EFEMP1 protein, also known as S1-5, FBNL, or fibulin-3, is a 493-amino acid protein in the fibulin family of extracellular matrix proteins. EFEMP1 is a secreted extracellular matrix protein, however, its function remains unknown.
In the normal human retina, EFEMP1 protein localizes outside the apical membrane of the retinal pigment epithelial (RPE) cells, in the region of the photoreceptor inner and outer segments. However, in retinas from ML and AMD patients, EFEMP1 localizes to a region between the RPE and drusen.
Adeno-associated virus (AAV) is the smallest of known human viruses. There is no disease which has been to date associated with AAV. It incorporates into the host cell's genome, but there is no evidence that it can cause malignant transformation. Because of these features it presents an attractive subject for creating vectors for gene therapy.
AAV advantages for gene therapy include: the lack of pathogenicity, the ability to infect non-dividing cells and the ability to stably integrate into the host cell genome at a specific site (designated AAVS1) in the human 19th chromosome. The last feature makes it superior to retroviruses, which present threat of a random insertion and of mutagenesis, which is sometimes followed by development of a cancer. The AAV genome integrates most frequently into the site mentioned, while random incorporations into the genome take place with a negligible frequency. AAVs also present very low immunogenicity, restricted only to generation of neutralizing antibodies, while they induce no cytotoxic response.